I would like to check on which actionEvent has occurred with ActionEvent e and e.getSource(). Can I use a switch case for this?
public void actionPerformed(ActionEvent e){
switch(e.getSource()){
case radius:
double r = validate(radius.getText());
break;
case height:
double h = validate(height.getText());
break;
case out:
out.setText(String.valueOf(h*r));
break;
}
}
Yes, you can use switch in actionPerformed.
No, you can't use it like you showed it here.
switch only supports primitive types and enums (and String, but only in Java 7 and later).
Another problem is that the case-values values must be compile time constants.
You'll need code like this:
public void actionPerformed(ActionEvent e){
if (e.getSource() == radius) {
double r = validate(radius.getText());
else if (e.getSource() == height) {
double h = validate(height.getText());
else if (e.getSource() == out) {
out.setText(String.valueOf(h*r));
}
}
No, you can't. The types you can use in a switch statement is very limited. See The switch Statement.
You can of course just write this as a series of "if" and "else if" statements.
As other solutions have pointed out, you cannot use switch in this context. However, rather than implementing one ActionListener containing a big if-then block, why not implement separate ActionListeners for each event source? This is a much more OO-based approach.
Typically your ActionListener implementations would be (small) anonymous inner classes anyway, and hence you wouldn't have to deal with a huge proliferation of .java files.
The ActionEvent contains an ActionCommand field which is a String. If not set while creating the Button it defaults to the text of the button. You can use that instead.
Something like:
switch(e.getActionCommand()) {
case "Radius":
....
case "Height":
....
}
